Company Vice President William Weimer says FBI agents visited the Seabrook store on Friday, interviewed staff and checked its computers.

He says the amount of gunpowder that could be harvested from the kits would not have been enough to detonate the Boston bombs.

Walton says Tsarnaev paid $200 cash but scanned his driver's license into the company's computer system as required by store policy. Walton says the employee who handled the sale described it as a routine transaction.